aws-sender.js

const CLOUD_MESSAGER = {
  android: {
    messager: 'GCM',
    arn: process.env.AWS_SNS_ANDROID_ARN
  },
  ios: {
    messager: 'APNS',
    arn: process.env.AWS_SNS_IOS_ARN
  }
};

async function sender(os, token, message){

  const sns = new AWS.SNS();

  const platform = await new Promise(resolve => {
      sns.createPlatformEndpoint(
        {
          PlatformApplicationArn: process.env.AWS_SNS_ANDROID_ARN,
          Token: token[os]
        },
        (err, data) => {
          if (err) {
            logger.error(err);
            throw err;
          }
          logger.info(data);
          resolve(data);
        }
      );
    });
    
  const endpointArn = platform.EndpointArn;
  let payload = {
    default: 'this is default',
    [CLOUD_MESSAGER[os].messager]: message
  };

  // first have to stringify the inner APNS object...
  payload.GCM = JSON.stringify(payload.GCM);
  // then have to stringify the entire message payload
  payload = JSON.stringify(payload);
  
  return new Promise(resolve => {
        sns.publish(
          {
            Message: payload,
            MessageStructure: 'json',
            TargetArn: endpointArn
          },
          (err, data) => {
            if (err) {
              throw err;
            }
            resolve(data);
          }
        );
  
}